Relation between calcium intake, grip strength and bone mineral density in the forearms of girls aged 13 and 15

Abstract

OBJECTIVES: To evaluate whether there is an association between calcium intake in adolescent girls and bone mineral density (BMD). Also, the relationships between BMD, various anthropometric factors and grip strength were evaluated. DESIGN: Cross-sectional comparison of BMD, calcium intake and grip strength in 13 and 15 year age groups, randomly selected. SETTING: Ten secondary elementary schools in the Reykjavik area. SUBJECTS: One hundred and ninety-seven Icelandic Caucasian girls aged 13 and 15. One hundred and seventy participated and 162 completed the study. MAIN OUTCOME MEASURES: Single photon absorptiometry was used to measure BMD and bone mineral content (BMC) in both forearms. Consumption of milk and dairy products was assessed using a food frequency questionnaire. Height and weight were measured and grip strength was determined with a hand-held dynamometer. RESULTS: Calcium intake was found to be significantly correlated to BMD in the older group after adjustment for menarcheal age and weight (r = 0.24; P < 0.05). Division into three subgroups yielded a significantly greater coefficient of correlation between calcium intake and BMD in the lowest calcium consumption group (r = 0.44; P < 0.05). No association was found in the younger age group. Significant positive correlations between grip strength and regional bone mineral density accounted for up to 16.8% of the variation in BMD (P < 0.001) and 38.4% of the variation in BMC. CONCLUSIONS: This study is consistent with the hypothesis that a threshold effect of calcium intake on BMD might exist. Above this threshold (1000-1200 mg) no further effect on BMD was seen. The results show a strong association between grip strength, a measure representative of total body strength, and BMD.